Mounting assembly for rectifiers

ABSTRACT

An assembly for mounting a plurality of rectifiers to a pair of current conductors. The conductors are two overlying plates, separated by a layer or sheet of insulation between their inner faces. Each rectifier is a high-current device in the form of an annular washer, and is mounted to an outer face of one of the conductors. The mounting means is a fastener having a shank which passes through one or a stack of the washer rectifiers, into an aperture extending perpendicularly to the conductors. The shank of the fastener is insulated from the conductor against which the rectifier is held, but is in electrical contact with the other conductor and is secured relative to both. A head or nut on the fastener exerts mechanical force on, and is in electrical contact with, the upper surface of the rectifier. The rectifying circuit includes the shank of the fastener.

United States Patent [451 Jan. 18,1972

Kruer [54] MOUNTING ASSEMBLY FOR RECTIFIERS [72] Inventor: Harold H.Kruer, Ft. Mitchell, Ky. [73] Assignee: Teledyne Mid-AmericaCorporation, Los

Angeles, Calif.

[22] Filed: Apr. 14, 1971 [21] App]. N0.: 133,821

[52] U.S.Cl ..317/234,317/10l [51] Int. Cl..... H011 1/12, H01l1/16 [58]Field oisearc ..3l7/234,234 B, 234 A,233

[56] References Cited UNITED STATES PATENTS 2,215,667 9/1940 Sherman..317/234 2,676,288 4/1954 Riley ...317/234 2,738,452 3/1956 Martin..3l7/234 2,992,372 7/1961 l-limeon et al. ..317/234 3,023,346 2/1962Wagner ..3l7/234 Att0rneyWo'od, Herron & Evans [57] ABSTRACT An assemblyfor mounting a plurality of rectifiers to a pair of current conductors.The conductors are two overlying plates, separated by a layer or sheetof insulation between their inner faces. Each rectifier is ahigh-current device in the form of an annular washer, and is mounted toan outer face of one of the conductors. The mounting means is a fastenerhaving a shank which passes through one or a stack of the washerrectifiers, into an aperture extending perpendicularly to theconductors. The shank of the fastener is insulated from the conductoragainst which the rectifier is held, but is in electrical contact withthe other conductor and is secured relative to both. A head or nut onthe fastener exerts mechanical force on, and is in electrical contactwith, the upper surface of the rectifier. The rectifying circuitincludes the shank of the fastener.

l 1 Claims, 2 Drawing Figures PATENTED JAN 1 8 I972 MOUNTING ASSEMBLYFOR RECTIFIERS This invention relates to a rectifier assembly which isespecially suited for mounting a large plurality of individualrectifiers to current conductors.

The invention finds particular utility in the fabrication ofhigh-amperage, low-voltage rectifying circuits of the type used inwelding equipment. While not inherently so limited, the invention isexplained hereinafter primarily in relation to such use.

Where currents of very high amperage, for example of the order of100,000 amperes, are rectified, a large plurality of rectifiers isusually used for the purpose. There are, of course, limits on thecurrent-handling capability of a single rectifier which such highcurrents would far exceed. Hence the current is divided and rectified inplural rectifying branch circuits so that no single rectifier exceedsits proper operating current range. For the standard present rectifiers,current limits are commonly about 500-],000 amperes, and it is thusapparent that to handle a total current load of 50,000 to 100,000amperes, anywhere from 50 to 100 rectifiers in parallel would beprovided.

In such use rectifiers are conventionally mounted to provide parallelflow paths between the conductors. For that purpose there are presentlyavailable clamps which exert a holding force on each rectifier to insuregood electrical contact.

Such rectifier holding and clamping means are relatively expensive; andwhere a large number of them must be used, they substantiallyincreasethe overall cost of the rectifying assembly. Moreover, they arerelatively bulky and require an unduly large volume of space.

It is the purpose of this invention to provide a simplified form ofrectifier mounting means, compact in size and economical to fabricate,and quickly attachable, which can accommodate as many parallelrectifying circuits as are desired for a particular installation.

In the present invention the current carrying electrodes comprise a pairof conductive plates, in overlapping or superimposed relation, withinsulating means between them. The insulating means may comprise anairgap, but is preferably a sheet or layer of dielectric material. Theconductor plates act as bus bars for carrying the heavy current to andfrom the rectifiers, to be described, in which the current is convertedto pulsating direct current. They also function as heat sinks. Channelscan be provided for coolant flow in one or the other of the conductorplates, or in the insulation or gasket between them.

The individual rectifiers are in the form of annular washers throughwhich the current passes generally perpendicularly, from one largesurface to the other. Each washer rectifier has a central hole throughwhich passes a combination current carrier and fastener. The fastenersmay take a number of forms, as will become apparent.

The conductor plates are preferably formed as a standardized subassemblywith mounting sites for accommodating a large number of rectifiers, asmay be needed.

The fasteners provide both an electrical connection to the rectifier,and mechanical connection of the plates. in preferred form it comprisesa bolt which is threaded into one plate. At each rectifier mountingposition an aperture is provided in the conductor plate subassembly,perpendicular to the surface thereof. The fastener passes through thehole in the washer rectifier and through the aperture in one plate,against which it holds the rectifier. 'l'he shank of the fastener isinsulated from this plate, to preclude current bypassing of therectifier, but is in electrical contact with the second conductor plate,i.e., the other plate than that on which the rectifier resides. Theshank of the fastener may be threaded into the aperture in the secondrectifier plate, or fastened by a nut on the other side of the secondplate.

As previously stated,-the fastener is a current carrying element of thecircuit. It provides the flow path between the second plate (the otherplate than that on which the rectifier resides), and one surface of therectifier. The other surface of the rectifier is connected to the firstplate. Thus current passes between the first conductor plate, therectifier, the shank of the fastener, and the second conductor plate.

Rectifying devices in the form of annular washers have previously beendescribed, as shown in the US. Pats. to Dooley, No. 1,748,0l2; Ruben No.1,865,213; Ray No. 2,383,735; Tumulo No. 2,637,77l; Burton No.2,751,528; and Howard No. 3,235,783. Bolts passing through apertures insuch rectifier washers have previously been used mechanically to clampthe rectifiers together in electrical contact with one another, orbetween spaced mounts.

This invention differs from the prior constructions in that here thefasteners constitute not only the mechanical mounting means for therectifiers, but also comprise an integral central part of the electricalcurrent path between the conductor plates. Moreover, in this invention,the conductor plates are facially juxtaposed, and constitute a multiplyapertured, preformed subassembly for the mounting of a plurality ofrectifiers directly on a single exposed surface thereof. This is adistinct advantage in tenns of ease of mounting, cost, size, andadaptability for accommodating various numbers of rectifiers.

The chemical nature of suitable rectifying components is well known inthe art, and does not form a part of this invention. By way of example,known rectifier materials include the conventional silicon andgermanium, as well as the older copper oxide rectifiers. Siliconrectifiers are most commonly used for high current installations.

The invention can best be further explained in relation to theaccompanying drawings in which:

FIG. 1 is a view in perspective of a preferred form of rectifierassembly in accordance with the invention, showing a large number ofrectifier washers mounted to a preformed conductor plate subassembly;and

FIG. 2 is an axial vertical section through a single rectifier as shownin FIG. 1, showing a current flow path in diagrammatic form.

The conductor plate subassembly is designated at 10 in FIGS. 1 and 2,and in preferred embodiment comprises two large flat rectangular copperplates, a first or upper plate 11 and a second or lower plate 12. Theseplates may be coextensive in area as shown, or may overlay partially,and they are connected to a source of potential by suitable means notshown. These plates are sized in cross-sectional area to carry currentsof the largest magnitude which is likely to be encountered.

The FIG. 2 it can be seen that insulating means in the form of adielectric sheet 13 is interposed between plates 11 and 12, to preventcurrent short circuiting between them which would bypass the rectifiersto be described. lf voltages involved are not high, for example, if theyare of the magnitudes involved in welding circuits, this insulation may,for example, comprise a sheet of cork. As will be seen, this layer mayalso function as a gasket for the coolant.

Nonconductive rivets or other fasteners 15 may be provide to hold theplates 11 and 12 together, pending insertion of the rectifier fasteners.I

A number of apertures 15 are spaced in a regular pattern over the upperface of plate subassembly 10. Each aperture 15 passes entirely throughthe upper plate 11, and preferably extends at least part way into lowerplate 12, sufficiently that the fastener may be mechanically secured toit as by threads. In the preferred embodiment shown, the upper plate 11has an aperture 16 which is of larger diameter than the aperture 17 inthe lower plate 12, and the latter aperture extends entirely through thelower plate. The portion 17 of the aperture in lower plate 12 isthreaded to engage threads 20 on a fastener designated generally at 19.

The fastener 19 is shown for purposes of illustration as a bolt. Itcomprises a shank portion 22 and an enlarged head portion 23. Thefastener 19 is a current-conducting component of the assembly, and forthat purpose may be made of copper. The mechanical load on it is usuallynot severe, as will appear.

Each bolt 19 fastens one or a stack of rectifiers 25 to the conductorplate assembly 10. Each rectifier 25 is in the form of a fiat annularwasher having an upper surface 26 and a lower surface 27. One of thesesurfaces is a rectifying surface, for example copper oxide, such thatcurrent flowing from one surface 26 or 27 to the other surface 27 or 26is rectified. The washer rectifier 25 has a hole 28 formed centrally init, through which the shank 22 of fastener 19 extends. It is thefunction of each fastener 19 when threaded into mechanical engagementwith one of the .conductor plates 11 or 12, to hold the rectifier 25 inelectrical contact with the upper conductor plate 1 l, by exerting acompression force thereon. It is also the function. of the fastener toprovide a current path through the hole 28 in the rectifier, through(but not to) aperture 16 in the first plate 11, to second plate 12. Thefastener 19 may also, and preferably does, mechanically connect the twoplates 11 and 12. In the embodiment shown, the fastener is in electricalcontact with only the top surface 26 of rectifier 25 and the secondplate 12, and is insulated from the hole 28 in the rectifier and theaperture 16 in the first plate 11.

For the purpose of providing good electrical contact, and avoidingtorque damage to the rectifier, a contact washer 30 may overlie theupper surface 26 of the rectifier 25, and a spring washer 31 may be usedbetween the head 23 of fastener 19 and contact washer 30.

It is important to note that an insulating layer or sheath 33 resides inaperture 16 in the first plate 11, to prevent flow of current directlyfrom fastener shank 22 to that conductor plate, which would bypass therectifier. For this reason aperture 16 is sized to accommodate thissheath 33, see FIG. 2. For low-voltage installations, this insulator 33may comprise a vinyl coating in aperture 16 or on the external surfaceof fastener 19 in the axial region within aperture 16, or it may simplycomprise a short length of tubing of insulating material which isdisposed within the aperture but not physically integral with it or thefastener. It extends to sheet 13 at its lower end, and projects abovethe top surface of plate 11, through the hole 28 in the rectifier washerto the upper surface 26 of the latter.

The arrows in FIG. 2 illustrate in diagrammatic form a current flow pathfrom lower plate 12 through threads 20 into the shank 22 of the fastener19, upwardly through the shank and into the head 23 thereof, outwardlyand downwardly through the spring washer 31, the contact washer 30,through the rectifying surfaces 26 and 27, and into the upper plate 11,(Depending on circumstances, current flow may be in the reversedirection, and it will be appreciated that the path shown is forpurposes of explanation only).

From the foregoing, those skilled in the art will recognize that thefastener 19, the contact and spring washers 30 and 31, if such are used,should be sized to accommodate the current densities which they willpass in use.

In the embodiment shown, only asingle rectifier 25 is mounted by eachfastener 19. In some cases (depending on the voltages involved and thevoltage limits of the rectifiers), a stack of several rectifier washersmay be mounted by each fastener. In this case the fastener head 23contacts the uppermost rectifier and the shank is insulated from thelower rectifiers in the stack, to prevent shorting.

Where it is desirable to provide cooling to minimize the temperaturerise in operating a large bank of rectifiers, coolant channels 35 can beprovided. As shown in FIG. 2, these channels are conveniently formed asgrooves in one of the conductor plates 11 or 12, which is closed by acover. The cover may conveniently be the insulating sheet 13.Altematively, coolant channels may be formed within the sheet 13. Thechannels trace a sinuous coolant course between the apertures 15.

In practice standardized conductor plate subassemblies with aperturesperformed in them can be carried as stock items by the manufacturer ofwelding equipment. The plates are held together by the rivets 14, untilfurther united by the installation of the fasteners. Rectifiers can thenbe fastened at as many mounting positions on the assembly 10 as areneeded for a given installation. The rectifiers can be mounted rapidly,simply by placing the desired number of rectifiers on the shank of afastener with the spring washer 31 and contact washer 30 first placedthereon, fitting a sheath 33 into the hole 28 within the washer, andsecuring and tightening these components in apertures 16 and 17.Depending on current requirements, not all of the apertures 15 providedon the subassembly 10 may be fitted with rectifiers (note the unusedapertures in FIG. 1). A housing to prevent shock, mechanical damage,accumulation of dirt and so on will usually be provided over theassembly.

In the foregoing explanation the fastener 19 has been described as abolt threaded into the second plate, and having an integral headexerting force on the rectifier. It will be apparent that other combinedmechanical fastening and electrical connecting means may be used. Forexample, an upwardly projecting stud threaded into the second plate mayhave a nut on its upper or free end to exert the holding force on therectifier. Alternately, a bolt passing through both plates may have anut threaded to it on either end to provide the desired force ontherectifier, electrical contact being made between the bolt and thesecond plate.

Having described the invention, what is claimed is:

1. A rectifier assembly comprising,

a first conductor plate facially overlying a second conductor plate butelectrically insulated from second plate by an insulator between them,

an aperture extending through said first plate,

a rectifier having parallel opposed first and second surfaces andadapted to rectify alternating current flowing from one said surface tothe other,

said rectifier disposed with one of its said surfaces in electricalcontact with the outer face of said first plate,

said rectifier having a hole therethrough perpendicular to its saidsurfaces, said hole being in line with said aperture,

a rectifier fastener having a shank extending through the hole in therectifier and through the aperture in the first plate, said fastenermaking an electrical contact with said second plate through said shank,

said fastener including a portion mechanically engaging one of saidplates to prevent axial movement with respect thereto,

said fastener also having means connected to said shank,

outwardly of said rectifier which exerts an axial compression forceholding said rectifier in physical and electrical engagement with theouter face of said first plate,

and insulating means around and within the aperture through said firstplate, said insulating means electrically insulating said first platebut not said second plate from the shank of said fastener, such thatcurrent can flow between said plates only by passing through both saidrectifier and the shank of said fastener.

2. The assembly of claim 1 wherein said fastener is a bolt havingthreads on the shank thereof which are engaged with cooperating threadson one of said plates.

3. The assembly of claim 1 wherein said aperture extends at least partway into said second plate, and the shank of said fastener extendsthereinto and is secured mechanically to said second plate.

4. The assembly of claim 3 wherein said fastener comprises a bolt havingthreads engaged with the aperture in said second plate and thereby holdssaid plates together and said rectifier to said plates.

5. The assembly of claim 1 wherein the insulating means around andwithin said aperture through the first plate comprises a layer ofinsulation extending from the inner face of the first plate through theaperture in the first plate to the outer face thereof.

6. The assembly of claim 1 wherein said insulating means around theaperture extends around the shank of said fastener, through the hole insaid rectifier.

7. The assembly of claim 1 wherein said first and second plates are heldin the overlying relation by nonconducting securing means, in additionto said fastener.

8. The assembly of claim 1 wherein a plurality of such apertures areformed in spaced array over the face of said first plate, and wherefasteners of the type described mount rectifiers of the type describedin some but not all of the said apertures.

9. A rectifier assembly comprising,

a first conductor plate facially overlying a second conductor plate butelectrically insulated and spaced from said second plate by a sheet ofinsulation between them,

an aperture extending through said first and second plates and saidsheet of insulation,

a washer rectifier having parallel opposed surfaces and adapted torectify alternating current flowing from one of said surfaces to theother,

said rectifier disposed with one of its aid surfaces in electricalcontact with the outer face of said first plate,

said rectifier having a hole therethrough perpendicular to its saidsurfaces, and which is in line with said aperture,

a current conductive bolt having a shank and a head, said shankextending through the hole in the rectifier, through the aperture in thefirst plate and sheet and threaded into the aperture in said secondplate,

the head of said bolt exerting a compression force holding saidrectifier in secure physical and electrical engagement with the outerface of said first plate, said bolt also holding said first plate infixed relation to said second plate,

and insulating means within the aperture through said first plate, saidinsulating means electrically insulating said first plate but not saidsecond plate from the shank of said bolt such that current can flowbetween said plates only by passing through bolt said rectifier and theshank of said securing means.

10. The rectifier assembly of claim 9 wherein the insulating meanswithin the aperture in the first plate comprises a tube of insulatingmaterial around the shank of said bolt.

11. The rectifier assembly of claim 10 wherein the aperture within saidfirst plate is oversized with respect to the aperture in the secondplate, to accommodate said tube.

1. A rectifier assembly comprising, a first conductor plate faciallyoverlying a second conductor plate but electrically insulated fromsecond plate by an insulator between them, an aperture extending throughsaid first plate, a rectifier having parallel opposed first and secondsurfaces and adapted to rectify alternating current flowing from onesaid surface to the other, said rectifier disposed with one of its saidsurfaces in electrical contact with the outer face of said first plate,said rectifier having a hole therethrough perpendicular to its saidsurfaces, said hole being in line with said aperture, a rectifierfastener having a shank extending through the hole in the rectifier andthrough the aperture in the first plate, said fastener making anelectrical contact with said second plate through said shank, saidfastener including a portion mechanically engaging one of said plates toprevent axial movement with respect thereto, said fastener also havingmeans connected to said shank, outwardly of said rectifier which exertsan axial compression force holding said rectifier in physical andelectrical engagement with the outer face of said first plate, andinsulating means around and within the aperture through said firstplate, said insulating means electrically insulating said first platebut not said second plate from the shank of said fastener, such thatcurrent can flow between said plates only by passing through both saidrectifier and the shank of said fastener.
 2. The assembly of claim 1wherein said fastener is a bolt having threads on the shank thereofwhich are engaged with cooperating threads on one of said plates.
 3. Theassembly of claim 1 wherein said aperture extends at least part way intosaid second plate, and the shank of said fastener extends thereinto andis secured mechanically to said second plate.
 4. The assembly of claim 3wherein said fastener comprises a bolt having threads engaged with theaperture in said second plate and thereby holds said plates together andsaid rectifier to said plates.
 5. The assembly of claim 1 wherein theinsulating means around and within said aperture through the first platecomprises a layer of insulation extending from the inner face of thefirst plate through the aperture in the first plate to the outer facethereof.
 6. The assembly of claim 1 wherein said insulating means aroundthe aperture extends around the shank of said fastener, through the holein said rectifier.
 7. The assembly of claim 1 wherein said first andsecond plates are held in the overlying relation by nonconductingsecuring means, in addition to said fastener.
 8. The assembly of claim 1wherein a plurality of such apertures are formed in spaced array overthe face of said first plate, and where fasteners of the type describedmount rectifiers of the type described in some but not all of the saidapertures.
 9. A rectifier assembly comprising, a first conductor platefacially overlying a second conductor plate but electrically insulatedand spaced from said second plate by a sheet of insulation between them,an aperture extending through said first and second plates and saidsheet of insulation, a washer rectifier having parallel opposed surfacesand adapted to rectify alternating current flowing from one of saidsurfaces to the other, said rectifier disposed with one of its aidsurfaces in electrical contact with the outer face of said first plate,said rectifier having a hole therethrough perpendicular to its saidsurfaces, and which is in line with said aperture, a current conductivebolt having a shank and a head, said shank extending through the hole inthe rectifier, through the aperture in the first plate and sheet andthreaded into the aperture in said second plate, the head of said boltexerting a compression force holding said rectifier in secure physicaland electrical engagement with the outer face of said first plate, saidbolt also holding said first plate in fixed relation to said secondplate, and insulating means within the aperture through said firstplate, said insulating means electrically insulating said first platebut not said second plate from the shank of said bolt such that currentcan flow between said plates only by passing through bolt said rectifierand the shank of said securing means.
 10. The rectifier assembly ofclaim 9 wherein the insulating means within the aperture in the firstplate comprises a tube of insulating material arounD the shank of saidbolt.
 11. The rectifier assembly of claim 10 wherein the aperture withinsaid first plate is oversized with respect to the aperture in the secondplate, to accommodate said tube.